choosing the right test - continuing medical education questions for choosing the right test 1. can...

5/28/2013

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Choosing the Right Cardiac Test

Atif Qasim, M.D., M.S.C.E.

University of California, San Francisco

Disclosures: None

2013

Outline

• Focus on choosing the optimal tests for coronary disease evaluation

• Overview of stress testing, imaging options and how tests are performed

• Instructive case scenarios with discussion

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Test the Audience

Which one of the following is true regarding stress testing?

• A. All patients who can exercise should have an exercise stress test (with/without imaging as appropriate).

• B. Patients undergoing conventional SPECT nuclear stress testing need to be able to lie flat.

• C. Beta blockers do not need to be stopped prior to a Dobutamine stress test.

• D. Patients with COPD cannot have a vasodilator stress test.

To Stress or not to Stress

• A paradigm shift has occurred for management of most stable CAD with medical therapy first rather than routine PCI.

• Significant cost and harm is associated with unnecessary testing, false positives, and additional procedures.

• Information from stress testing should be meaningful to direct management.

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Broad Indications for Stress Testing

• For diagnosis and risk stratification in those with suspected CAD, or known CAD with a change in clinical status.

• Assess location and degree of ischemia in those with known CAD for the purposes of revascularization.

• Determine if medical therapy and/or revascularization therapy is adequate for CAD.

• Evaluate severity and symptoms of valvular or congenital heart disease or evaluate arrhythmic therapy (non CAD related).

Contraindications ‐ Question

Which of the follow is not an absolute contraindication to stress testing?

A. Acute myocarditis

B. Decompensated heart failure

C. Acute MI

D. Severe uncontrolled hypertension

E. Symptomatic severe aortic stenosis

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Contraindications

Absolute

• Acute MI within 2 days, or active unstable angina

• Symptomatic severe aortic stenosis

• Decompensated heart failure

• Aortic dissection

• Acute myocarditis or pericarditis

• Uncontrolled arrhythmias

• Acute PE

Relative

• Left main disease

• Severe uncontrolled hypertension

• Hypertrophic obstructive cardiomyopathy

• High degree AV block

How does stress testing work?

• Different tests interrogate different portions of this ischemic cascade.

• Each method employs a “stressor” and a “detector.”

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Mix and Match

Stressors

• Exercise

– Treadmill

– Supine bike

• Vasodilator

– Adenosine

– Dipyridamole

– Regadenoson

• Dobutamine

Detectors• EKG (used for all tests)

• Echocardiography

• Radionuclide imaging– Thallium 201, Technetium99M

• PET

• MRI

Exercise on Treadmill

• Need to get to 85% max predicted HR (220‐age), for an optimal test

• Usual Bruce Protocol starts at 1.7mph at a 10% grade and increases in speed and grade every 3 minutes.

• Test may be stopped early for significant chest pain, severe hypertensive or hypotensive response, marked ST changes, or arrhythmia.

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Exercise on Supine Bike

• Allows for echo imaging in real time during different phases of exercise

• Graded protocol with increase in workload every 3 minutes

• Good for valvular disease assessment in those who are functional, but cannot use the treadmill

Pharmacologic Stressors ‐ Vasodilators

‐ Increases coronary blood flow 3 to 5 fold in normal arteries

‐ Diseased arteries do not augment flow well

‐ Effects can be reversed with aminophyllineafter radiotracer injection

‐ Contraindicated with active bronchospasm, high grade AV block, & significant hypotension

• Adenosine – A2A (coronary vasodilation),– A1 (AV delay),– A2B, A3, A4 (bronchospasm) – Short half life

• Dipyridamole (Persantine)– Blocks re‐uptake of adenosine– Longer half life

• Regadenoson– Selective A2A agonist– Shorter half life than

Dipyridamole

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Pharmacologic Stressors ‐ Dobutamine

• Infusion protocol is with escalating doses of dobutamine in 3 min increments

• Goal to get to target HR of 85% max predicted

• Atropine (vagolytic) and hand/leg exercises are also used to augment heart rate

• Positive inotrope and chronotrope (ß1)

• Also some vasodilation properties (ß2)

• Contraindicated in those with arrhythmias, significant hypertension, and marked LV outflow obstruction

Detectors ‐ EKG

• Consistent horizontal or downsloping ST depressions in contiguous leads is positive

• ST depressions do not localize diseased vessel

• Not always a binary yes/no outcome. Can have equivocal/non diagnostic results

ACC/AHA Guidelines 2001

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Question ‐ EKG

In which of the following is treadmill EKG only (i.e. no imaging) stress testing still appropriate?

A. Left Bundle Branch Block

B. LVH with repolarization abnormality

C. WPW

D. Ventricular pacing

E. Digoxin use

F. Right Bundle Branch Block

When should you consider imaging?

• Baseline EKG is abnormal or uninterpretablefor ischemia

• Known CAD or prior revascularization with change in clinical symptoms (localize ischemia)

• Another question to be assessed (LV function, viability, hemodynamic significance of valvular disease, changes in PASP with exercise)

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Nuclear Scanner

• Patient emits radioactivity which is detected by one or more “cameras.”

• Cameras rotate slowly around the patient to generate a 3D image of the heart.

• Patient must lie flat up to 20‐30 min and not move.

• Artifact can occur from motion, and tissue attenuation.

Nuclear Images

Normal Stress Abnormal Stress

Stress

Rest

Rest

Rest

Stress

Stress

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Echo imaging

Other Considerations

• Radiation Dosage

• Cost– Treadmill EKG< Stress echo < Cardiac CT Angio< SPECT < Coronary Angiogram

• Special patient populations (CT surgery, post transplant, obese, etc)

• Local expertise

Source: www.scai.org

Echo/EKG None

Chest X ray (for comparison) 0.1mSv

Coronary Angiogram 7mSv (~15 if intervention done)

Cardiac CT Angiography 10‐16mSv

Nuclear Stress ‐ Tc‐99 11mSv

Nuclear Stress – Thallium 17mSv

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Test Pros Cons

Exercise EKG

Cost effective No radiationPrognostic information from exercise

False positivesDoesn’t localize ischemiaLess sensitive/specific

Vasodilator with SPECT

Easy to administerGood for those with arrhythmias or hypertension

RadiationMust lie flat/stay still Balanced ischemia possibleAttenuation artifacts

Exercise or Dobutaminewith Echo

No radiationHeart function, structure, valves, diastology , PASP also assessed

Baseline wall motion makes interpretation harderPoorer image quality in obese

Vasodilator with PET

Higher resolution, less artifactUseful in those who are obeseViability when FDG usedQuicker nuclear based study

RadiationShort half life of radiotracer limits stressor modalities

Vasodilatorwith MRI

Heart anatomy, structure, function, infarct size , location, viability all can be assessed

Need expertise, timeBreath holding, lie flat & still Regular HR ideal

Viability Studies

• Use in those with known CAD, prior or recent infarct, LV dysfunction

• To see if revascularization is reasonable to improve LV function

• Several options– Dobutamine Echo

– Rest‐redistribution thallium

– PET/CT – look for FDG uptake

– MRI – look for extent of delayed enhancement

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When to Consider Cardiac Cath

• High risk unstable angina

• A high pretest probability of CAD

• Positive stress test with large burden of reversible ischemia

• Failure of medical management for CAD

• Concern for an ischemic cardiomyopathy

• Preoperative assessment for cardiac valve surgery or high risk transplantation surgery

When to consider a Cardiac CT

• Acute chest pain with low probability of disease (ER setting)

• When there is a non diagnostic stress or when clinical findings and stress tests results are incongruous

• When a coronary anomaly is suspected

• To assess bypass graft patency or if there is a question about graft anatomy

• When traditional stress tests cannot be performed

• Limited use if there is renal insufficiency, tachycardia, arrhythmia, or too much coronary artery calcium

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Case 1

A 60 yr old male with diabetes, hypertension, and COPD on home oxygen and theophylline who has chest pain. He has severe chronic back pain and cannot lie flat.

Which stress test is most appropriate?

A. Exercise EKGB. Exercise stress echoC. Exercise nuclear D. Dobutamine stress echoE. Dobutamine nuclearF. Vasodilator nuclear G. Curbside the cardiologist

Case 2

A 62 yr old man with hypertension, hypercholesterolemia and atypical chest pain, that sometimes happens during exercise, but also at rest. He has known chronic Left Bundle Branch Block.



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Case 3

A 45 yr old female with diabetes, on dialysis and s/p BKA, admitted with chest pain, and ruled out for MI by EKG and cardiac enzymes.



Case 4

A 45 year old woman with moderate RA affecting hands primarily and mild resting pulmonary hypertension who complaints of chest pain and dyspnea on exertion?



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Case 5

A 46 yr old mildly obese diabetic female who wants to start an exercise program to lose weight.



Case 6

A 68 yr old man with chronic atrial fibrillation on digoxinand metoprolol who has chest pain.



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Case 7

A 69 yr old male with chest pain, who has significant knee osteoarthritis and an ischemic cardiomyopathy with a known EF of 40% .



Case 8

A 48 year old 450 lb morbidly obese woman with OSA on CPAP and h/o prior DVT, who complaints of atypical chest pain that is relieved with nitroglycerin. She is not very mobile and cannot lie completely flat.



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Medications Prior to Stress

• Vasodilator Test ‐ Hold Theophylline, Pentoxifylline (Trental), and Dipyridamole 48 hrs before‐ Hold all caffeine 12 hrs before‐ Viagra (24hrs before), Cialis (72hrs before), Nitrates (48 hrs before), CCBs (48hrs before)

• Exercise or Dobutamine Test– Beta blockers/ Diltiazem/Verapamil (48hrs before)

• Oral diabetes medications – hold in the am• Do not hold anti anginal medications if goal is to assess for effectiveness of medical therapy

Key Questions for Choosing the Right Test

1. Can the patient exercise?2. Is the baseline EKG normal?3. Does the patient have known CAD or arrhythmias?

4. Any comorbid conditions (bronchospasm, heart block, cardiomyopathy, etc)?

5. Are they on medications that can interfere with the type of test?

6. Why are you performing the test and what will you do with the results?

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Test the Audience ‐ Answer

Which one the following is true?• A. All patients who can exercise should have an exercise stress test (with/without imaging as appropriate).

• B. Patients undergoing conventional SPECT nuclear stress testing need to be able to lie flat.

• C. Beta blockers do not need to be stopped prior to a Dobutamine stress test.

• D. Patients with COPD cannot have a vasodilator stress test.

Further Reading

1. Gibbons RJ, Balady GJ, Bricker JT, et al. ACC/AHA 2002 guideline update for exercise testing: summary article. J Am Coll Cardiol 2002; 40:1531.

2. Hendel RC, Berman DS, Di Carli MF, et al. ACCF/ASNC/ACR/AHA/ASE/SCCT/SCMR/SNM 2009 Appropriate Use Criteria for Cardiac Radionuclide Imaging. J Am Coll Cardiol 2009; 53:2201.

3. ACCF/ASE/AHA/ASNC/HFSA/HRS/SCAI/SCCM/SCCT/SCMR 2011 Appropriate Use Criteria for Echocardiography. J Am Soc Echocardiogr2011; 24:229.

4. Douglas PS , Khandheria B, Stainback R. et al. ACCF/ASE/ACEP/AHA/ASNC/SCAI/SCCT/SCMR 2008 Appropriateness Criteria for Stress echocardiography. Circulation. 2008;117:1478‐1497

5. Fraker TD Jr, Fihn SD, et al. Chronic Stable Angina Writing Committee: focused update of the ACC/AHA 2002 guidelines for the management of patients with chronic stable angina: J Am Coll Cardiol. 2007;50(23):2264.

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